Phenomenological constraints on low-scale gravity

Abstract

We study the constraints on gravity scale ${M}_{P}$ in extra-dimension gravitational theory, obtained from gravity-induced processes. The obtained constraints are subdivided into strong (though not robust) and reliable (though less strong). The strong constraints can be in principle relaxed due to some broken gauge symmetries, e.g. family symmetry. The strongest constraint is given by neutrino oscillations. For different assumptions the lower bound on ${M}_{P}$ is ${10}^{15}--{10}^{18}\text{ }\text{ }\mathrm{GeV}$. However, it can be, in principle, reduced by broken family symmetry. More reliable bounds are due to flavor-conserved operators or those which change the flavors within one family. These bounds, obtained using the electron mass and width of $\ensuremath{\pi}\ensuremath{\rightarrow}e\ensuremath{\nu}$ decay, are $1\ifmmode\times\else\texttimes\fi{}{10}^{5}\text{ }\text{ }\mathrm{GeV}$ and $5\ifmmode\times\else\texttimes\fi{}{10}^{5}\text{ }\text{ }\mathrm{GeV}$, for these two cases, respectively.